Snowmobile having a gearbox

ABSTRACT

A snowmobile has a two-stroke engine having an electronic reverse function so that a crankshaft can be selectively rotated in forward and reverse rotation directions. A gearbox has a first shaft coupled to a countershaft, a second shaft extending parallel to the first shaft, first transmission gears mounted to the first shaft and second transmission gears mounted to the second shaft. The first transmission gears are in constant mesh with the second transmission gears to form high and low gear pairings. A shifter is operable for selectively operating the gearbox in one of a high gear, a low gear and a neutral gear. The engine is selectively operable in the forward and reverse rotation directions while the gearbox is operated in at least one of the high gear, the low gear and the neutral gear.

CROSS-REFERENCE

The present application claims priority from U.S. Provisional PatentApplication No. 62/868,491, filed on Jun. 28, 2019, the entirety ofwhich is incorporated herein by reference.

TECHNICAL FIELD

The present technology relates to snowmobile transmissions.

BACKGROUND

A snowmobile's engine is operatively connected to a drive track of thesnowmobile to propel the snowmobile. Different transmission componentsare connected between the engine and the drive track to control a speedand torque applied at the drive track. Namely, a continuous variabletransmission (CVT) is typically connected to the engine and provides avariable transmission ratio.

However, while transmission components such as the CVT provide controlof the speed and torque at the drive track, a greater degree of controlof these parameters may be desired by a user of the snowmobile.Moreover, while some snowmobile engines are provided with a reversefunction which allows the engine to operate in reverse, othersnowmobiles engines may not be provided with such a reverse function andthus the snowmobile could benefit from other ways of operating inreverse.

Therefore, there is a need for a snowmobile that addresses at least someof these drawbacks.

SUMMARY

It is an object of the present technology to ameliorate at least some ofthe inconveniences present in the prior art.

In accordance with an aspect of the present technology, there isprovided a snowmobile. The snowmobile includes: a frame; at least oneski connected to the frame; a rear suspension assembly connected to theframe; a drive track disposed around the rear suspension assembly; and atwo-stroke internal combustion engine supported by the frame. The enginehas a crankshaft. The engine has an electronic reverse function foroperating the engine in reverse so that the crankshaft can beselectively rotated in a forward rotation direction and a reverserotation direction. The snowmobile also includes a continuously variabletransmission (CVT) operatively connected to the crankshaft. The CVTincludes a drive pulley operatively connected to the crankshaft, adriven pulley, and a transmission belt interconnecting the drive pulleyand the driven pulley. The snowmobile also includes a countershaftconnected to the driven pulley of the CVT. The snowmobile also includesa gearbox. The gearbox includes: a first shaft coupled to thecountershaft; a second shaft extending parallel to the first shaft; aplurality of first transmission gears mounted to the first shaft; aplurality of second transmission gears mounted to the second shaft; anda housing enclosing the first and second transmission gears therein androtatably supporting the first shaft and the second shaft. Each of thefirst transmission gears is in constant mesh with a corresponding one ofthe second transmission gears to form a plurality of gear pairingsincluding a high gear pairing and a low gear pairing. For each of thehigh and low gear pairings: a given one of the first and secondtransmission gears is in selective free-spin engagement with acorresponding one of the first shaft and the second shaft to which thegiven one of the first and second transmission gears is mounted; and another one of first and second transmission gears is in fixed engagementwith a corresponding one of the first shaft and the second shaft towhich the other one of the first and second transmission gears ismounted. The snowmobile also includes a driveshaft coupled to the secondshaft of the gearbox, the driveshaft being operatively connected to thedrive track to propel the snowmobile; and a shifter operable by a userfor selectively operating the gearbox in one of a high gear, a low gearand a neutral gear, such that: when the gearbox operates in the highgear, the shifter engages the given one of the first and secondtransmission gears corresponding to the high gear paring to causedriving engagement thereof with the corresponding one of the first shaftand the second shaft; when the gearbox operates in the low gear, theshifter engages the given one of the first and second transmission gearscorresponding to the low gear pairing to cause driving engagementthereof with the corresponding one of the first shaft and the secondshaft; and when the gearbox operates in the neutral gear, the shifter isdisengaged from the first and second transmission gears so that thegiven one of the first and second transmission gears of each of the highand low gear pairings remains in free-spin engagement with thecorresponding one of the first shaft and the second shaft. The engine isselectively operable in one of the forward rotation direction and thereverse rotation direction while the gearbox is operated in at least oneof the high gear, the low gear and the neutral gear.

In some embodiments, the gearbox also includes: a countershaft gearmounted to the countershaft and enclosed within the housing of thegearbox; and a driven gear fixedly mounted to the first shaft, enclosedwithin the housing of the gearbox, and in rotational engagement with thecountershaft gear so that the first shaft is coupled to thecountershaft.

In some embodiments, the gearbox also includes: a driving sprocketfixedly mounted to the second shaft and enclosed within the housing ofthe gearbox; an output sprocket fixedly mounted to the driveshaft andenclosed within the housing of the gearbox; and a flexible drivingmember drivingly connecting the driving sprocket to the output sprocketso as to transmit rotary motion from the second shaft to the driveshaft.

In some embodiments, the flexible driving member is a belt.

In some embodiments, the given one of the first and second transmissiongears of each of the high and low gear pairings in selective free-spinengagement with a corresponding one of the first shaft and the secondshaft is the first transmission gears such that: the first transmissiongears are in selective free-spin engagement with the first shaft; andthe second transmission gears are in fixed engagement with the secondshaft.

In some embodiments, the shifter includes: a shifter knob movablebetween a high gear position, a low gear position and a neutral gearposition corresponding to the high gear, the low gear and the neutralgear of the gearbox respectively; a dog mounted on the first shaft andslidable along an axis of the first shaft, the dog comprising dog teeth;and a plurality of links interconnecting the dog to the shifter knob.Each of the first transmission gears has dog teeth matching the dogteeth of the dog. When the shifter knob is moved to the high gearposition, the dog engages the dog teeth of the first transmission gearcorresponding to the high gear pairing. When the shifter knob is movedto the low gear position, the dog engages the dog teeth of the firsttransmission gear corresponding to the low gear pairing. When the shiftknob is moved to the neutral gear position, the dog is disengaged fromthe first transmission gears.

In some embodiments, in the neutral gear position of the shifter knob,the dog is mounted on the first shaft between the first transmissiongear corresponding to the high gear pairing and the first transmissiongear corresponding to the low gear pairing.

In some embodiments, the shifter also includes a support bracket forsupporting the shifter knob. The support bracket is fastened to thehousing of the gearbox.

In some embodiments, the housing of the gearbox includes a left housingportion and a right housing portion. The left and right housing portionsare affixed to one another.

In some embodiments, the first shaft defines a first shaft axis aboutwhich the first shaft is rotatable; the second shaft defines a secondshaft axis about which the second shaft is rotatable; and the firstshaft axis is vertically higher than the second shaft axis.

In some embodiments, the driveshaft defines a driveshaft axis aboutwhich the driveshaft is rotatable. The second shaft axis is verticallyhigher than the driveshaft axis.

In some embodiments, the first transmission gears and the secondtransmission gears are helical gears.

In some embodiments, the gearbox is disposed on a right side of theengine.

In some embodiments, the CVT is disposed on a left side of the engine.

In some embodiments, the countershaft extends from the left side of theengine to the right side of the engine.

In some embodiments, the snowmobile also includes a pair of drivesprockets mounted to the driveshaft. The drive sprockets are in drivingengagement with the drive track.

In some embodiments, the low gear pairing is disposed laterally betweenthe high gear pairing and the CVT.

In some embodiments, the low gear pairing is disposed laterally betweenthe countershaft gear and the high gear pairing.

In some embodiments, the low gear pairing is disposed laterally betweenthe high gear pairing and the driven gear.

In some embodiments, the driven gear is disposed leftwardly of the lowgear pairing.

In some embodiments, the driving sprocket is disposed laterally betweenthe low gear pairing and the CVT.

In some embodiments, the low gear pairing is disposed laterally betweenthe high gear pairing and the driving sprocket.

In some embodiments, the gearbox also includes: a driving sprocketfixedly mounted to the second shaft and enclosed within the housing ofthe gearbox, the driving sprocket being disposed laterally between thecountershaft gear and the low gear pairing; an output sprocket fixedlymounted to the driveshaft and enclosed within the housing of thegearbox; and a flexible driving member drivingly connecting the drivingsprocket to the output sprocket so as to transmit rotary motion from thesecond shaft to the driveshaft.

In some embodiments, the snowmobile also includes a handlebaroperatively connected to the at least one ski for steering the a leastone ski, and a control element located on the handlebar for selectivelyactivating the electronic reverse function of the engine.

In some embodiments, the control element is a push button.

For purposes of this application, terms related to spatial orientationwhen referring to the vehicle orientation and positioning of itscomponents such as forwardly, rearwardly, left, and right are as theywould normally be understood by a driver of the vehicle sitting thereonin a normal riding position.

Embodiments of the present technology each have at least one of theabove-mentioned aspects, but do not necessarily have all of them.

Additional and/or alternative features, aspects, and advantages ofembodiments of the present technology will become apparent from thefollowing description, the accompanying drawings, and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present technology, as well as otheraspects and further features thereof, reference is made to the followingdescription which is to be used in conjunction with the accompanyingdrawings, where:

FIG. 1 is a perspective view, taken from a rear, left side, of asnowmobile;

FIG. 2 is a perspective view, taken from a rear, left side, of part ofthe snowmobile of FIG. 1, including an engine, a continuous variabletransmission (CVT), a gearbox, and a driveshaft;

FIG. 3 is a perspective view, taken from a rear, right side, of thegearbox and a countershaft of the snowmobile of FIG. 1, with a housingof the gearbox being open to expose various components of the gearbox;

FIG. 4 is a perspective view, taken from a front, right side, of part ofthe gearbox and the countershaft of the snowmobile of FIG. 1, with thegearbox being operated in a high gear;

FIG. 5A is a perspective view, taken from a front, right side, of thepart of the gearbox and the countershaft of FIG. 4, with the gearboxbeing operated in a neutral gear;

FIG. 5B is a perspective view, taken from a front, right side, of thepart of the gearbox and a countershaft FIG. 4, with the gearbox beingoperated in a low gear;

FIG. 6 is a top plan view of the gearbox and of a shifter of thesnowmobile of FIG. 1;

FIG. 7 is a perspective view, taken from a rear, left side, of thegearbox and the countershaft in accordance with another configuration ofthe snowmobile;

FIG. 8 is a front elevation view of the gearbox and the countershaft ofthe configuration of the snowmobile of FIG. 7;

FIG. 9 is a left side elevation view of the gearbox and the countershaftof the configuration of the snowmobile of FIG. 7;

FIG. 10 is a perspective view, taken from a rear, left side, of part ofthe CVT, the countershaft and the gearbox of the configuration of thesnowmobile of FIG. 7, with a left portion of the housing of the gearboxremoved to expose internal components of the gearbox;

FIG. 11 is a top plan view of the components of the snowmobile of FIG.10;

FIG. 12 is a front elevation view of part of the gearbox and thecountershaft in accordance the configuration of the snowmobile of FIG.7, in which the gearbox is in a reverse operation mode;

FIG. 13 is a rear elevation view of the part of the gearbox and thecountershaft of FIG. 10, in which the gearbox is in the reverseoperation mode;

FIG. 14 is a front elevation view of the part of the gearbox and of thecountershaft of FIG. 7, in which the gearbox is in a forward operationmode;

FIG. 15 is an exploded view, taken from a rear, right side, of part ofthe gearbox, part of the countershaft of the configuration of thesnowmobile of FIG. 7.

DETAILED DESCRIPTION

With reference to FIG. 1, a snowmobile 100 will be described herein. Thesnowmobile 100 has a front end 102 and a rear end 104, which are definedconsistently with the forward travel direction of the vehicle. Thesnowmobile 100 includes a frame 106 which includes a tunnel 108.

A ski and steering assembly is provided, in which two skis 116 (only oneof which is shown in FIG. 1) are positioned at the front end 102 of thesnowmobile 100, and are attached to a front portion of the frame 106through a front suspension assembly 118.

The front suspension assembly 118 includes ski legs 120, supporting arms122, spindles and ball joints for operatively joining the respective skilegs 120, supporting arms 122 and a steering column 124. The supportingarms 122 include left and right upper A-arms 117 and left and rightlower A-arms 119 (only left upper and lower A-arms 117, 119 being shownin FIG. 1). It is contemplated that the front suspension assembly 118could be different from the double A-arm suspension described above. Atits upper end, the steering column 124 is attached to a handlebar 126which is positioned forward of a user to rotate the ski legs 120 andthus the skis 116, in order to steer the snowmobile 100.

A straddle seat 138 is disposed rearward of the handlebar 126. A rearportion 139 of the straddle seat 138 provides a passenger seat. Twofootrests 140 (only one of which is shown in FIG. 1) extend alongopposite lateral sides of the snowmobile 100 below the straddle seat 138to accommodate the riders' feet.

An engine 114 (FIG. 2) is supported by the frame 106. In thisembodiment, the engine 114 operates on a two-stroke engine cycle suchthat the engine 114 completes a power cycle with two strokes (anupstroke and a downstroke) of the engine's pistons (not shown). Theengine 114 can thus be referred to as a two-stroke engine. Withreference to FIG. 2, the engine 114 has a crankcase 130, a cylinderblock 132 defining two cylinders (not shown) connected on top of thecrankcase 130 and a cylinder head 142 connected on top of the cylinderblock 132. The engine 114 also has a crankshaft (not shown) disposed inthe crankcase 130 and driven by the motion of the pistons.

The engine 114 has an electronic reverse function for operating theengine 114 in reverse so that the crankshaft can be selectively rotatedin a forward rotation direction and a reverse rotation direction. Thisis achieved by controlling the fuel injection and ignition within thecylinders of the engine 114. For instance, U.S. Pat. No. 5,036,802,issued Aug. 6, 1991, which is incorporated herein by reference,describes in detail a manner in which this electronic reverse functioncan be achieved. The electronic reverse function can be selectivelyactivated via an electronic reverse function control element 150 (FIGS.1, 2) disposed on the handlebar 126 of the snowmobile 100. In thisembodiment, the electronic reverse function control element 150 is apush button which is selectively actuated by the user to engage ordisengage the electronic reverse function of the engine 114.

As shown in FIG. 2, the engine 114 is connected to a continuouslyvariable transmission (CVT) 160 disposed on a left side of the engine114. The CVT 160 includes a drive pulley 162 operatively connected tothe crankshaft of the engine 114, a driven pulley 164 disposed on acountershaft 165 for rotation therewith, and a transmission belt 167disposed around both pulleys 162, 164 to transmit torque from the drivepulley 162 to the driven pulley 164. The driven pulley 164 is rearwardand upward of the drive pulley 162 such that the countershaft 165 islocated rearward and upward of the crankshaft of the engine 114. A cover(not shown) covers the pulleys 162, 164 and the transmission belt 167.

Each of the pulleys 162, 164 includes a movable sheave that can moveaxially relative to a fixed sheave to modify an effective diameter ofthe corresponding pulley 162, 164. The drive pulley 162 is a centrifugalpulley in that the sheaves thereof move in response to a centrifugalforce applied thereon. The effective diameters of the pulleys 162, 164are in inverse relationship. In the illustrated embodiment, the CVT 160is a purely mechanical CVT 160, in which the diameter of the drivepulley 162 increases with increasing rotational speed of the drivepulley 162 (i.e., with increasing engine speed). The diameter of thedriven pulley 164 therefore decreases when the torque required at thecountershaft 165 increases. The CVT 160 may thus be referred to as an“unassisted” CVT in that a gear ratio of the CVT 160 (i.e., an effectivediameter of the driven pulley 164 over the effective diameter of thedrive pulley 162) is automatically mechanically adjusted in accordancewith the speed of the engine 114 and the torque requirement at thecountershaft 165.

It is contemplated that, in other embodiments, the CVT 160 could be anassisted CVT such as a hydraulic CVT.

A gearbox 170 disposed on the right side of the engine 114 is connectedto the CVT 160 via the countershaft 165 such that the countershaft 165extends from the left side to the right side of the engine 114. Thegearbox 170, which will be described in greater detail below, provides agearing system which allows the driver of the snowmobile 100 to change a“gear” in which the gearbox 170 is operated. Moreover, as will bedescribed below, in some embodiments, the gearbox 170 can be operated in“reverse”.

It is contemplated that, in other embodiments, the positions of the CVT160 and the gearbox 170 could be switched such that the CVT 160 isdisposed on the right side of the engine 114 and the gearbox 170 isdisposed on the left side of the engine 114.

Returning to FIG. 1, at the front end 102 of the snowmobile 100,fairings 134 are provided that enclose the engine 114, the CVT 160, andthe gearbox 170, thereby providing an external shell that not onlyprotects these components of the snowmobile 100, but also make thesnowmobile 100 more aesthetically pleasing. The fairings 134 include ahood 135 and one or more side panels which can be opened to allow accessto the engine 114, the CVT 160 and the gearbox 170 when this isrequired, for example for inspection or maintenance thereof. Awindshield 136 is connected to the fairings 134 in front of thehandlebar 126. Alternatively, the windshield 136 can be attacheddirectly to the handlebar 126. The windshield 136 acts as a windscreento lessen the force of the air on the user while the snowmobile 100 ismoving forward.

An endless drive track 128 is disposed under the tunnel 108. The endlessdrive track 128 is operatively connected to the engine 114 through theCVT 160 and the gearbox 170. The endless drive track 128 is driven torun about a rear suspension assembly 131 for propulsion of thesnowmobile 100.

The rear suspension assembly 131 comprises front and rear shockabsorbers (not shown). The front shock absorber extends rearwardly anddownwardly from a front portion of the tunnel 108, and is disposedbetween the tunnel 108 and a slide frame assembly 144, partially forwardof front suspension arms of the rear suspension assembly 131. The rearshock absorber extends forwardly and downwardly from a rear portion ofthe tunnel 108, and is disposed at least in part rearwardly of the frontsuspension arms. The slide frame assembly 144 includes a pair of spacedapart slide rails 146 that engage the inner side of the ground-engagingportion of the endless drive track 128. The slide frame assembly 144journals a plurality of backup rollers 133 and four idler rollers 137.In addition, further rollers are carried by the tunnel 108, in order todefine the path over which the endless drive track 128 travels. Othertypes of rear suspension assemblies are contemplated.

The endless drive track 128 is engaged with and driven by two drivesprockets 152 (FIG. 2) which are journaled by the tunnel 108 and aredriven by the engine 114 via the CVT 160 and the gearbox 170. Morespecifically, the drive sprockets 152 are mounted to a driveshaft 175which is operatively connected to the gearbox 170.

At the rear end 104 of the snowmobile 100, a snow flap 163 is connectedto a rear end of the tunnel 108. The snow flap 163 protects againstsnow, ice, dirt or other debris that could be projected from the drivetrack 128 when driving. In some embodiments, the snow flap 163 alsoredirects snow and ice projected by the drive track 128 on the undersideof the tunnel 108 where an engine heat exchanger (not shown) isprovided. It is contemplated that the snow flap 163 could be omitted.

The snowmobile 100 includes other elements well known in the art, and assuch they will not be described in detail herein.

The gearbox 170 and related components of the snowmobile 100 will now bedescribed with reference to FIGS. 3 to 6.

The gearbox 170 includes a primary shaft 172, a secondary shaft 174, anda plurality of gears mounted to a respective one of the primary and thesecondary shafts 172, 174. A housing 176 of the gearbox 170 encloses theprimary and secondary shafts 172, 174 and their respective gearstherein. The housing 176 includes a left portion 178 and a right portion180 which are affixed to one another to enclose the components of thegearbox 170.

As briefly mentioned above, the countershaft 165 operatively connectsthe CVT 160 to the gearbox 170. In this embodiment, the countershaft 165extends partly within the housing 176 of the gearbox 170 to drivinglyengage the gearing of the gearbox 170. In particular, the countershaft165 extends through a left portion 178 of the housing 176 and isrotatably supported by the housing 176 via two bearings 182 (FIG. 4)mounted to the countershaft 165, one of which is mounted to an end ofthe countershaft 165. The bearing 182 mounted to the end of thecountershaft 165 is supported by the right portion 180 of the housing176 and the other bearing 182 is supported by the left portion 178 ofthe housing 176. In order to drive the gearbox 170, a forward drive gear184 is mounted to the countershaft 165 and rotates therewith. Notably,in this embodiment, the forward drive gear 184 is in driving engagementwith a splined portion 186 of the countershaft 165. Furthermore, in thisembodiment, the forward drive gear 184 is a single gear mounted to thecountershaft 165 to drive the gearbox 170.

The countershaft 165 may alternatively be referred to as an “inputshaft” as it transmits the input rotary motion into the gearbox 170.Similarly, the driveshaft 175 may alternatively be referred to as an“output shaft” as it transmits the output rotary motion from the gearbox170.

The primary shaft 172 defines a primary shaft axis A1 extendinglaterally (i.e., parallel to the countershaft axis CA) about which theprimary shaft 172 is rotatable. In particular, the primary shaft 172 isrotatably mounted to the housing 176 via bearings 188 mounted to theends of the primary shaft 172. Notably, one of the bearings 188 mountedto a right end of the primary shaft 172 is supported by the rightportion 180 of the housing 176 and the other bearing 188 mounted to aleft end of the primary shaft 172 is supported by the left portion 178of the housing 176. The primary shaft 172 is positioned rearward of thecountershaft 165 such that the primary shaft axis A1 is rearward of thecountershaft axis CA. Moreover, the primary shaft axis A1 is verticallyhigher than the countershaft axis CA. A forward driven gear 190 ismounted to the primary shaft 172 and rotates therewith. A splinedconnection is implemented between the forward driven gear 190 and asplined portion of the primary shaft 172. In this embodiment, thegearbox 170 is driven by the countershaft 165 via the forward drivengear 190. More specifically, the forward driven gear 190 is inrotational engagement with the forward drive gear 184 so that theprimary shaft 172 is coupled to the countershaft 165.

Two primary transmission gears 192L, 192H are mounted to the primaryshaft 172 and are spaced from one another. The primary transmissiongears 192L, 192H are used to transmit motion from the primary shaft 172to the secondary shaft 174. In particular, as will be described below,one of the primary transmission gears 192L, 192H is selected to transmitmotion to the secondary shaft 174 in accordance with a desired torqueand speed. To that end, the primary transmission gears 192L, 192H areconfigured differently. Notably, the primary transmission gear 192L issmaller in diameter than the primary transmission gear 192H.

In this embodiment, the primary transmission gears 192L, 192H are inselective free-spin engagement with the primary shaft 172. Inparticular, the primary transmission gear 192L is loosely fitted to theprimary shaft 172, while the primary transmission gear 192H is mountedto the primary shaft 172 via a needle bearing 193 (FIG. 15). As such, ontheir own, the primary transmission gears 192L, 192H and the primaryshaft 172 are drivingly disengaged. It is contemplated that, in otherembodiments, the primary transmission gear 192L could be rotatablymounted to the primary shaft 172 via a bearing, or the primarytransmission gear 192H could be loosely fitted to the primary shaft 172.As will be described in greater detail below, a shifter 200 is used toselect which of the primary transmission gears 192L, 192H, if any, toplace into driving engagement with the primary shaft 172. In order toengage the shifter 200, each of the primary transmission gears 192L,192H has dog teeth 195 (shown for the primary transmission gear 192L inFIG. 4) which are engaged by the shifter 200 when one of the primarytransmission gears 192L, 192H is selected to be placed into drivingengagement with the primary shaft 172. In particular, the primarytransmission gear 192L has the dog teeth 195 on its right side (i.e.,facing the primary transmission gear 192H) while the primarytransmission gear 192H has the dog teeth 195 on its left side (i.e.,facing the primary transmission gear 192L).

A deflector 194 is fastened to the housing 176 and partially surrounds apart of the primary shaft 172. The deflector 194 is configured todeflect lubricant (i.e., oil) which is projected from a flexible drivingmember 206 towards the primary transmission gears 192L, 192H. Theforward driven gear 190 and the primary transmission gears 192L, 192Hare disposed on opposite sides of the deflector 194.

The secondary shaft 174 defines a secondary shaft axis A2 extendingparallel to the primary shaft axis A1 (i.e., laterally) and about whichthe secondary shaft 174 is rotatable. In particular, the secondary shaft174 is rotatably mounted to the housing 176 via bearings 196 mounted tothe ends of the secondary shaft 174. Notably, one of the bearings 196mounted to a right end of the secondary shaft 174 is supported by theright portion 180 of the housing 176 and the other bearing 196 mountedto a left end of the secondary shaft 174 is supported by the leftportion 178 of the housing 176. As can be seen in FIG. 4, the primaryshaft axis A1 is vertically higher than the secondary shaft axis A2. Thesecondary shaft axis A2 is also vertically lower than the countershaftaxis CA. Moreover, the secondary shaft axis A2 is disposed rearwardly ofthe primary shaft axis A1 and rearwardly of the countershaft axis CA.

Two secondary transmission gears 198L, 198H are mounted to the secondaryshaft 174 and are spaced from one another. In this embodiment, thesecondary transmission gears 198L, 198H are in fixed engagement with thesecondary shaft 174 (i.e., the secondary transmission gears 198L, 198Hare drivingly engaged by the secondary shaft 174). The secondarytransmission gear 198L has a greater diameter than the secondarytransmission gear 198H.

In this embodiment, the primary and secondary transmission gears 192L,192H, 198L, 198H are helical gears.

It is contemplated that, in other embodiments, the secondarytransmission gears 198L, 198H could be in selective free-spin engagementwith the secondary shaft 174 while the primary transmission gears 192L,192H are in fixed engagement with the primary shaft 172. For example, insuch embodiments, the secondary transmission gears 198L, 198H areprovided with the dog teeth instead of the primary transmission gears192L, 192H, and the shifter 200 is connected to the secondary shaft 174to selectively engage one of the secondary transmission gears 198L,198H.

The primary and secondary transmission gears 192L, 198L, are in constantmesh with one another to form a low gear pairing 202L. The primary andsecondary transmission gears 192H, 198H, are in constant mesh with oneanother to form a high gear pairing 202H. These gear pairings 202L, 202Hcan be selectively chosen, via the shifter 200, to transmit rotarymotion from the countershaft 165 to the driveshaft 175 in order toaffect the speed and torque at the driveshaft 175. Notably, as will beunderstood, the gear pairings 202L, 202H offer different gear ratios fortransmitting motion from the primary shaft 172 to the secondary shaft174. For instance, the low gear pairing 202L is selected to transmitmotion from the primary shaft 172 to the secondary shaft 174 when agreater torque is desired, whereas the high gear pairing 202H isselected to transmit motion from the primary shaft 172 to the secondaryshaft 174 when a greater speed is desired. As such, the high gearpairing 202H is associated with a “high gear” of the gearbox 170 whilethe low gear pairing 202L is associated with a “low gear” of the gearbox170. The gearbox 170 is thus described as operating in high gear whenthe shifter 200 engages the high gear pairing 202H (FIG. 4) and asoperating in low gear when the shifter 200 engages the low gear pairing202L (FIG. 5B). As will be described in more detail below, the gearbox170 can also be operated in “neutral gear” whereby none of the gearpairings 202L, 202H are engaged by the shifter 200 (i.e., the primarytransmission gears 172L, 172H are disengaged by the shifter 200) (FIG.5A).

It is contemplated that the gearbox 170 could be operated in additionalgears (e.g., a second high gear, a second low gear) by providingadditional gear pairings.

The shifter 200 can thus be operated by the user to place one of theprimary transmission gears 192L, 192H of a selected one (or none) of thegear pairings 202L, 202H into driving engagement with the primary shaft172 (via the matching dog teeth 195, 242 as described above) which inturn engages the corresponding secondary transmission gear 198L, 198H.

In this embodiment, the high gear pairing 202H is disposed rightwardlyof the low gear pairing 202L. As such, the low gear pairing 202L isdisposed laterally between the high gear pairing 202H and the CVT 160.The low gear pairing 202L is also disposed laterally between the forwarddrive gear 184 and the high gear pairing 202H. Similarly, the low gearpairing 202L is disposed laterally between the high gear pairing 202Hand the forward driven gear 190. As such, the forward driven gear 190 isdisposed leftwardly of the low gear pairing 202L.

As shown in FIG. 3, a driving sprocket 204 is fixedly mounted to thesecondary shaft 174 and enclosed within the housing 176. The drivingsprocket 204 is disposed leftwardly of the secondary transmission gears198L, 198H and is generally laterally aligned with the divider 194. Inparticular, the driving sprocket 204 is disposed laterally between thelow gear pairing 202L and the CVT 160. As such, the low gear pairing202L is disposed laterally between the high gear pairing 202H and thedriving sprocket 204.

The driving sprocket 204 is operatively connected to the driveshaft 175.Notably, the flexible driving member 206 drivingly connects the drivingsprocket 204 to an output sprocket 208 fixedly mounted to the driveshaft175 and enclosed within the housing 176. As such, rotary motion istransmitted from the secondary shaft 174 to the driveshaft 175 via thedriving and output sprockets 204, 208 and the flexible driving member206. The driveshaft 175 is thus coupled to the secondary shaft 174.

The driveshaft 175 defines a driveshaft axis DA about which thedriveshaft 175 and the output sprocket 208 are rotatable. The driveshaftaxis DA is vertically lower than and rearward of the secondary shaftaxis A2 about which the driving sprocket 204 rotates.

The flexible driving member 206 may be any suitable type of flexibledriving member. In this embodiment, the flexible driving member 206 is achain which engages the teeth of the sprockets 204, 208. In otherembodiments, the flexible driving member 206 may be a rubber belt forexample. Moreover, an adjustable tensioner 210 (FIG. 4) is provided toregulate tension in the flexible driving member 206. In this embodiment,the tensioner 210 applies pressure on an outer side of the flexibledriving member 206. The tensioner 210 is supported by the housing 176.

As shown in FIGS. 3 to 5B, a speed sensor 213 is supported by thehousing 176 and is configured to measure the speed of the driveshaft175.

As shown in FIG. 4, a configurable portion 212 of the secondary shaft174 extends leftwardly from the driving sprocket 204 (and thusleftwardly of the second transmission gears 198L, 198H). In particular,the configurable portion 212 extends laterally between the forward drivegear 184 and an inner wall of the housing 176 defined by the leftportion 178 of the housing 176. In this configuration of the snowmobile100, the configurable portion 212 of the secondary shaft 174 is free ofany gears mounted thereto. As will be discussed in greater detail below,in another configuration of the snowmobile 100, a gear is mounted to theconfigurable portion 212 of the secondary shaft 174 for transmittingrotary motion to the secondary shaft 174 otherwise than through theprimary shaft 172 (i.e., without going through the primary shaft 172).Likewise, the countershaft 165 has a configurable portion 185 extendinglaterally between the forward drive gear 184 and an inner wall of thehousing 176 defined by the left portion 178 of the housing 176. As such,the configurable portion 185 extends leftwardly of the forward drivegear 184. Similarly to the configurable portion 212 of the secondaryshaft 174, in this configuration of the snowmobile 100, the configurableportion 185 of the countershaft 165 is free of any gears mountedthereto. The configurable portions 185, 212 of the countershaft 165 andthe secondary shaft 174 are laterally aligned with one another.

The shifter 200 is operable by the user of the snowmobile 100 forselectively operating the gearbox in one of the high gear, the low gearand a neutral gear. With reference to FIGS. 4 to 5B, the shifter 200includes a shifter knob 220, a dog 222, and a link assembly 224interconnecting the dog 222 to the shifter knob 220. The shifter 200also has a support bracket 223 for supporting the shifter knob 220. Thesupport bracket 223 is fastened to the housing 176.

With reference to FIG. 6, the shifter knob 220 is movable betweendifferent positions to select a gear in which to operate the gearbox170. More specifically, the shifter knob 220 is movable between a highgear position, a low gear position and a neutral gear positioncorresponding to the high gear, the low gear and the neutral gear of thegearbox 170 respectively. As shown in FIG. 4, the shifter knob 220 has aknob portion 225, a base portion 226 and a shaft 228 interconnecting theknob portion 225 to the base portion 226. The knob portion 225 isconfigured to be handled by the user's hand. A connector 234 of the baseportion 226 is connected to the dog 222 via the link assembly 224. Thebase portion 226 defines a pivot 230 at its bottom end, implemented viaa rod end 232. The shifter knob 220 is pivotable frontwardly andrearwardly about the pivot 230. The shifter knob 220 is moved leftwardlyor rightwardly to a selected one of the high gear, low gear and neutralgear positions. Notably, as can be seen in FIG. 6, a path of the shifterknob 220 is from left to right as it moves from the high gear position,to the neutral gear position and to the low gear position in order tocause the dog 222 to move accordingly laterally along the primary shaft172. A shifter cover 235 (FIG. 6) covers part of the shifter 200, withthe knob portion 225 and the shaft 228 protruding through an aperture237 of the shifter cover 235. The aperture 237 defines the path of theshifter knob 220 as it is moved through the different gear positions. Ascan be seen from the aperture 237, once the shifter knob 220 is in thecorrect position for the desired gear, the shifter knob 220 is movedforwardly along a corresponding longitudinal-extending portion of theaperture 237 so that the gearbox 170 stays engaged in the selected gear.To that end, a spring 239 (FIGS. 5A, 5B) is provided at the pivot 230 tobias the shifter knob 220 forwardly and into thelongitudinally-extending portion of the aperture 237 corresponding tothe selected gear. In order to change gears, the shifter knob 220 isthus moved rearwardly (against the biasing force of the spring 239) todisengage the corresponding longitudinally-extending portion of theaperture 237 and then moved laterally to another gear position.

The link assembly 224 includes a generally laterally-extending link 236,a generally longitudinally-extending link 238 and an interconnectingbracket 240 to which each of the links 236, 238 is connected. Thelaterally-extending link 236 has one end fastened to the connector 234of the base portion 226 of the shifter knob 220. Another end of thelaterally-extending link 236 is fastened to the interconnecting bracket240. The longitudinally-extending link 238 has one end fastened to theinterconnecting bracket 240 and the other end fastened to the dog 222.

The dog 222 is mounted on the primary shaft 172 and is slidable alongthe primary shaft axis A1. An inner part of the dog 222 is drivinglyengaged with the primary shaft 172 and thus rotates therewith. Notably,an inner periphery of the dog 222 is splined to engage the splines onthe primary shaft 172. A fork 229 (FIGS. 5A, 5B) of the dog 222 isrotatable relative to the inner part of the dog 222 and is connected tothe link 238. As shown in FIGS. 5A and 5B, the dog 222 has dog teeth 242on the left and right sides of the dog 222 which match the dog teeth 195of the primary transmission gears 192L, 192H. The dog teeth 242 of thedog 222 are configured to engage and thereby drive the primarytransmission gears 192L, 192H via the dog teeth 195 thereof.

Notably, when the shifter knob 220 is moved to the high gear position(FIG. 4), the dog 222 slides right and engages the dog teeth 195 of theprimary transmission gear 192H corresponding to the high gear pairing202H. When the shifter knob 220 is moved to the low gear position (FIG.5B), the dog 222 slides left and engages the dog teeth 195 of theprimary transmission gear 192L corresponding to the low gear pairing202L. When the shifter knob 220 is moved to the neutral gear position(FIG. 5A), the dog 222 slides to a position between the primarytransmission gears 192L, 192H and is disengaged from the primarytransmission gears 192L, 192H.

By operating the gearbox 170 via the shifter 220 and controlling therotation direction of the crankshaft of the engine 114 via the reversefunction control element 150, the user of the snowmobile 100 can chooseto operate the gearbox 170 in any of the high, low and neutral gearswhile the crankshaft of the engine 114 rotates in the forward rotationdirection or the reverse rotation direction. As such, the user may havea greater degree of control of the speed and torque delivered to thedrive track 128 when the snowmobile 100 moves in reverse. The gearbox170 is said to be in “reverse operation” when the crankshaft of theengine 114 rotates in the reverse rotation direction, namely since thedriveshaft 175, when rotating, rotates in a direction that is associatedwith rearward driving direction of the snowmobile 100 (when thehandlebar 126 is oriented to steer the skis 116 straight). In someembodiments, when the crankshaft of the engine 114 rotates in reverse,the gearbox 170 may be limited to operating in one or two of the high,low and neutral gears. For example, in some embodiments, when thecrankshaft of the engine 114 rotates in reverse, the gearbox 170 may belimited to operating in the low gear.

It is contemplated that the shifter knob 220 of the shifter 200 could bereplaced by an electric actuator which is operated by the user viabuttons (e.g., provided on the handlebar 126) such as to provideelectric shifting.

As will be described in greater detail below, the snowmobile 100 can beconfigured according to two different configurations. The two differentconfigurations of the snowmobile 100 implement different ways in whichthe reverse operation of the gearbox 170 can be achieved. An example ofthe first configuration of the snowmobile 100 is described above withrespect to FIGS. 3 to 6, whereby the reverse operation of the gearbox170 is achieved by operating the engine 114 in the reverse rotationdirection.

The second configuration of the snowmobile 100 that allows reverseoperation of the gearbox 170 will now be described below with respect toFIGS. 7 to 14. In the second configuration of the snowmobile 100, thesnowmobile 100 has an engine 314 (schematically illustrated in FIG. 7)which, unlike the engine 114, does not have an electronic reversefunction and thus the reverse operation of the gearbox 170 is providedby driving components of the snowmobile 100 other than the engine 314,namely including the gearbox 170. In this embodiment, in the secondconfiguration of the snowmobile 100, the engine 314 is a four-strokeengine operating on a four-stroke engine cycle such that the engine 314completes a power cycle with four strokes (two upstrokes and twodownstrokes) of the engine's piston(s). Indeed, the second configurationof the snowmobile 100 may be particularly useful for four-stroke enginesas their crankshafts can only be rotated in a single rotation direction.Alternatively, the engine 314 in the second configuration of thesnowmobile 100 could be a two-stroke engine which does not implement theelectronic reverse function described above.

As shown in FIG. 7, the engine 314 is operatively connected to thecountershaft 165 via the CVT 160 described above.

As shown in FIGS. 12 to 14, in the second configuration of thesnowmobile 100, the forward drive gear 184 is in selective free-spinengagement with the countershaft 165. As such, the forward drive gear184 drives the primary shaft 172 only when it is selected to do so.

Moreover, in the second configuration of the snowmobile 100, thesnowmobile 100 includes a reverse drive gear 246 mounted to thecountershaft 165 at the configurable portion 185 of the countershaft 165and in driving engagement with the countershaft 165. In particular, thereverse drive gear 246 is drivingly connected to the countershaft 165via a splined connection therebetween. The reverse drive gear 246 isenclosed within the housing 176 and, as will be described in greaterdetail below, is slidable along the countershaft 165. The reverse drivegear 246 also has dog teeth 252 extending from a right side thereof.Notably, in this second configuration of the snowmobile 100, the forwarddrive gear 184 has dog teeth 254 which are configured for matching thedog teeth 252 of the reverse drive gear 246. The dog teeth 254 of theforward drive gear 184 extend from a left side thereof (i.e., facing thereverse drive gear 246).

As can be seen in FIGS. 11, 12 and 14, a support collar 256 is rotatablyconnected to the reverse drive gear 246 on a left side thereof. That is,the support collar 256 can rotate relative to the reverse drive gear 246such that, when the reverse drive gear 246 rotates with the countershaft165, the support collar 256 remains in the same rotational positionabout the countershaft 165. As will be described in greater detailbelow, the support collar 256 allows connection of the reverse drivegear 246 to an actuator.

Furthermore, in the second configuration of the snowmobile 100, thegearbox 170 includes a reverse driven gear 248 mounted to the secondaryshaft 174 at the configurable portion 212 of the secondary shaft 174.More specifically, as shown in FIG. 15, the reverse driven gear 248 ismounted to the secondary shaft 174 via a needle bearing 257. However, anadapter 251 mounted to the secondary shaft 274 is splined to engage thesplines of the secondary shaft 174 and is drivingly connected to thereverse driven gear 248 via dog teeth 255 extending from a left side ofthe adapter 251. In particular, the reverse driven gear 248 has dogteeth 253 extending from a right side thereof and which match the dogteeth 255 of the adapter 251. The reverse driven gear 248 is configuredto mesh with the reverse drive gear 246. The reverse driven gear 248 isenclosed within the housing 176.

In this embodiment, the reverse drive gear 246 and the reverse drivengear 248 are spur gears.

In the second configuration of the snowmobile 100, an actuator 260 isprovided for selectively transmitting rotary motion from thecountershaft 165 to the gearbox 170 via a selected one of the forwarddrive gear 184 and the reverse drive gear 246. That is, the actuator 260is controlled by an input from the user to drive the gearbox 170 in aforward rotation direction (corresponding to rotational engagement ofthe forward drive gear 184) or in a reverse rotation direction(corresponding to rotational engagement of the reverse driven gear 248).To that end, in the second configuration, the reverse function controlelement 150 controls the actuator 260 rather than reverse operation ofthe engine as is the case in the first configuration. In particular, inthe second configuration of the snowmobile 100, the control element 150is selectively actuated by the user to set the actuator 260 to transmitrotary motion from the countershaft 165 to the gearbox 170 via one ofthe forward drive gear 184 and the reverse drive gear 246.

In this embodiment, the actuator 260 is an electric actuator. Inparticular, the electric actuator 260 comprises a motor 264 and alinkage assembly 266 which operatively connects the motor 264 to thereverse drive gear 246 via the support collar 256. Notably, as shown inFIGS. 11 and 12, the linkage assembly 266 includes a fork 263 havingconnecting arms 267 which are pivotably connected to the support collar256. The linkage assembly 266 is configured such that rotational motionof the motor 264 causes the support collar 256 to slide along thecountershaft 266. More specifically, with reference to FIGS. 10 to 12and 15, the linkage assembly 266 includes a driving lever 269 (FIGS. 10to 12) which is connected to a driving shaft of the motor 264 such as torotate therewith. The driving lever 269 is fastened to a generallyvertically-extending linkage 271, which in turn is fastened to agenerally laterally-extending linkage 273. The laterally-extendinglinkage 273 is fastened to a generally longitudinally-extending linkage274 which is connected to the fork 263. The rotating motion of thedriving lever 269 causes the linkages 271, 273, 274 to move such thatthe driving support collar 256 is moved along the countershaft 266.

It is contemplated that, in other embodiments, the actuator 260 could bea manually operated actuator, whereby the user manually operates theactuator 260 (e.g., via a handle) to selectively transmit rotary motionto the gearbox 170 via the forward drive gear 184 or the reverse drivegear 248. For instance, in such embodiments, the actuator 260 may evenbe incorporated by the shifter 200 whereby the shifter 200 is used tochange the gear in which the gearbox 170 operates (i.e., high, low,neutral gears) as well as to selectively place the gearbox 170 inreverse operation. For example, the shifter knob 220 could have a“reverse gear position” which, when engaged, causes the transmission ofrotary motion to the gearbox 170 via the reverse drive gear 248.

The actuator 260 is controlled by the user via the control element 150to operate the gearbox 170 in either a “forward operation mode” or a“reverse operation mode”. In the forward operation mode, illustrated inFIG. 14, rotary motion is transmitted from the countershaft 165 to thegearbox 170 via the forward drive gear 184 (i.e., the forward drive gear184 is in rotational engagement with the forward driven gear 190). Moreparticularly, when the control element 150 is controlled by the user toengage the forward operation mode of the gearbox 170, the actuator 260moves the reverse drive gear 246 along the countershaft 165 such thatthe dog teeth 252, 254 of the reverse and forward drive gears 246, 184are engaged with one another thereby transmitting rotary motion from thereverse drive gear 246 to the forward drive gear 184 which, as it ismeshed with the forward driven gear 190, drives the primary shaft 174.The manner in which motion is then transmitted to the driveshaft 175 (ifthe gearbox 170 is in the high or low gears) has been described aboveand thus will not be repeated here.

The forward operation mode is associated with a forward drivingdirection of the snowmobile 100 when the handlebar 126 is oriented tosteer the skis 116 straight. Notably, in the forward operation mode ofthe gearbox 170, the driveshaft 175, when rotating (i.e., in the highgear and low gear of the gearbox 170), rotates in the same direction asthe countershaft 165. Moreover, the gearbox 170 is operable in any ofthe high gear, the low gear and the neutral gear in the forwardoperation mode of the gearbox 170.

In the reverse operation mode, illustrated in FIGS. 12 and 13, rotarymotion is transmitted from the countershaft 165 to the gearbox 170 viathe reverse drive gear 246 (i.e., with the reverse drive gear 246driving the reverse driven gear 248). More particularly, when thecontrol element 150 is controlled by the user to engage the reverseoperation mode of the gearbox 170, the actuator 260 moves the reversedrive gear 246 along the countershaft 165 such that the reverse drivegear 246 is aligned with and is in rotational engagement with thereverse driven gear 248 thereby transmitting rotary motion from thereverse drive gear 246 to the reverse driven gear 248. As the reversedriven gear 248 is drivingly engaged to the secondary shaft 174, it isthe secondary shaft 174 that is coupled to the countershaft 165 in thereverse operation mode of the gearbox 170 rather than the primary shaft172 (as is the case in the forward operation mode). The driving sprocket204, which is also mounted to the secondary shaft 174, thus rotates anddrives the output sprocket 208 via the flexible driving member 206.Thus, in the reverse operation mode, the selected one of the high, lowand neutral gears of the gearbox 170 as set by the shifter 200 does notaffect the rotational output at the driveshaft 175 since rotary motionis not transmitted from the primary shaft 172 to the secondary shaft174.

The reverse operation mode is associated with a rearward drivingdirection of the snowmobile 100 when the handlebar 126 is oriented tosteer the skis 116 straight. Notably, in the reverse operation mode ofthe gearbox 170, the driveshaft 175, when rotating (which is at alltimes during the reverse operation mode), rotates in a reverse directionopposite to a direction of rotation of the countershaft 165.

As will be understood, the snowmobile 100 can be provided in the firstconfiguration or the second configuration with relative ease as most ofthe components are similar in both configurations. This may thus providea drivetrain platform for a snowmobile that can accommodate an enginehaving an electronic reverse function (i.e., a two-stroke engine) aswell as an engine which is not operable in reverse (e.g., a two-strokeor four-stroke engine) while using many of the same components. In turn,this may facilitate manufacturing of snowmobiles of both configurationsas fewer parts are needed to produce different models of the snowmobileand thus decrease associated costs.

Modifications and improvements to the above-described embodiments of thepresent technology may become apparent to those skilled in the art. Theforegoing description is intended to be exemplary rather than limiting.The scope of the present technology is therefore intended to be limitedsolely by the scope of the appended claims.

What is claimed is:
 1. A snowmobile, comprising: a frame; at least one ski connected to the frame; a rear suspension assembly connected to the frame; a drive track disposed around the rear suspension assembly; a two-stroke internal combustion engine supported by the frame, the engine comprising a crankshaft, the engine having an electronic reverse function for operating the engine in reverse so that the crankshaft can be selectively rotated in a forward rotation direction and a reverse rotation direction; a continuously variable transmission (CVT) operatively connected to the crankshaft, comprising: a drive pulley operatively connected to the crankshaft; a driven pulley; and a transmission belt interconnecting the drive pulley and the driven pulley; a countershaft connected to the driven pulley of the CVT; a gearbox comprising: a first shaft coupled to the countershaft; a second shaft extending parallel to the first shaft; a plurality of first transmission gears mounted to the first shaft; a plurality of second transmission gears mounted to the second shaft, each of the first transmission gears being in constant mesh with a corresponding one of the second transmission gears to form a plurality of gear pairings including a high gear pairing and a low gear pairing, for each of the high and low gear pairings: a given one of the first and second transmission gears being in selective free-spin engagement with a corresponding one of the first shaft and the second shaft to which the given one of the first and second transmission gears is mounted, an other one of first and second transmission gears being in fixed engagement with a corresponding one of the first shaft and the second shaft to which the other one of the first and second transmission gears is mounted; and a housing enclosing the first and second transmission gears therein and rotatably supporting the first shaft and the second shaft; a driveshaft coupled to the second shaft of the gearbox, the driveshaft being operatively connected to the drive track to propel the snowmobile; a shifter operable by a user for selectively operating the gearbox in one of a high gear, a low gear and a neutral gear, such that: when the gearbox operates in the high gear, the shifter engages the given one of the first and second transmission gears corresponding to the high gear paring to cause driving engagement thereof with the corresponding one of the first shaft and the second shaft; when the gearbox operates in the low gear, the shifter engages the given one of the first and second transmission gears corresponding to the low gear pairing to cause driving engagement thereof with the corresponding one of the first shaft and the second shaft; and when the gearbox operates in the neutral gear, the shifter is disengaged from the first and second transmission gears so that the given one of the first and second transmission gears of each of the high and low gear pairings remains in free-spin engagement with the corresponding one of the first shaft and the second shaft, the engine being selectively operable in one of the forward rotation direction and the reverse rotation direction while the gearbox is operated in at least one of the high gear, the low gear and the neutral gear.
 2. The snowmobile of claim 1, wherein the gearbox further comprises: a countershaft gear mounted to the countershaft and enclosed within the housing of the gearbox; and a driven gear fixedly mounted to the first shaft, enclosed within the housing of the gearbox, and in rotational engagement with the countershaft gear so that the first shaft is coupled to the countershaft.
 3. The snowmobile of claim 1, wherein the gearbox further comprises: a driving sprocket fixedly mounted to the second shaft and enclosed within the housing of the gearbox; an output sprocket fixedly mounted to the driveshaft and enclosed within the housing of the gearbox; and a flexible driving member drivingly connecting the driving sprocket to the output sprocket so as to transmit rotary motion from the second shaft to the driveshaft.
 4. The snowmobile of claim 3, wherein the flexible driving member is a chain.
 5. The snowmobile of claim 1, wherein: the given one of the first and second transmission gears of each of the high and low gear pairings in selective free-spin engagement with a corresponding one of the first shaft and the second shaft is the first transmission gears such that: the first transmission gears are in selective free-spin engagement with the first shaft; and the second transmission gears are in fixed engagement with the second shaft.
 6. The snowmobile of claim 5, wherein the shifter comprises: a shifter knob movable between a high gear position, a low gear position and a neutral gear position corresponding to the high gear, the low gear and the neutral gear of the gearbox respectively; a dog mounted on the first shaft and slidable along an axis of the first shaft, the dog comprising dog teeth; and a plurality of links interconnecting the dog to the shifter knob, wherein: each of the first transmission gears has dog teeth matching the dog teeth of the dog; when the shifter knob is moved to the high gear position, the dog engages the dog teeth of the first transmission gear corresponding to the high gear pairing; when the shifter knob is moved to the low gear position, the dog engages the dog teeth of the first transmission gear corresponding to the low gear pairing; and when the shifter knob is moved to the neutral gear position, the dog is disengaged from the first transmission gears.
 7. The snowmobile of claim 6, wherein, in the neutral gear position of the shifter knob, the dog is mounted on the first shaft between the first transmission gear corresponding to the high gear pairing and the first transmission gear corresponding to the low gear pairing.
 8. The snowmobile of claim 1, wherein the housing of the gearbox comprises a left housing portion and a right housing portion, the left and right housing portions being affixed to one another.
 9. The snowmobile of claim 1, wherein: the first shaft defines a first shaft axis about which the first shaft is rotatable; the second shaft defines a second shaft axis about which the second shaft is rotatable; and the first shaft axis is vertically higher than the second shaft axis.
 10. The snowmobile of claim 9, wherein the driveshaft defines a driveshaft axis about which the driveshaft is rotatable, the second shaft axis being vertically higher than the driveshaft axis.
 11. The snowmobile of claim 1, wherein the first transmission gears and the second transmission gears are helical gears.
 12. The snowmobile of claim 1, wherein the low gear pairing is disposed laterally between the high gear pairing and the CVT.
 13. The snowmobile of claim 2, wherein the low gear pairing is disposed laterally between the countershaft gear and the high gear pairing.
 14. The snowmobile of claim 2, wherein the low gear pairing is disposed laterally between the high gear pairing and the driven gear.
 15. The snowmobile of claim 14, wherein the driven gear is disposed leftwardly of the low gear pairing.
 16. The snowmobile of claim 3, wherein the driving sprocket is disposed laterally between the low gear pairing and the CVT.
 17. The snowmobile of claim 16, wherein the low gear pairing is disposed laterally between the high gear pairing and the driving sprocket.
 18. The snowmobile of claim 2, wherein the gearbox further comprises: a driving sprocket fixedly mounted to the second shaft and enclosed within the housing of the gearbox, the driving sprocket being disposed laterally between the countershaft gear and the low gear pairing; an output sprocket fixedly mounted to the driveshaft and enclosed within the housing of the gearbox; and a flexible driving member drivingly connecting the driving sprocket to the output sprocket so as to transmit rotary motion from the second shaft to the driveshaft.
 19. The snowmobile of claim 1, further comprising: a handlebar operatively connected to the at least one ski for steering the a least one ski; and a control element located on the handlebar for selectively activating the electronic reverse function of the engine.
 20. The snowmobile of claim 19, wherein the control element is a push button. 